Smart Membrane with Reversible Superwetting Transition for On-Demand Antifouling and Self-Cleaning

Membrane wettability is crucial for filtration performance when treating feedwater containing inorganic particles, organic macromolecules, and microorganisms. Superhydrophilic membranes excel in resisting fouling during filtration, while superhydrophobic membranes are prized for their self-cleaning properties during maintenance. To address these contrasting needs, we herein propose a novel strategy by developing membranes with switchable superhydrophilicity and superhydrophobicity, enabling on-demand antifouling and self-cleaning. This membrane was created by electrodepositing copper oxides onto a copper mesh, resulting in the formation of hierarchical micro- and nanoscale structures. By applying a reduction voltage of -20 V, the copper oxides were converted into hydrophilic metallic copper, transforming the mesh into a superhydrophilic membrane. This transformation not only facilitated water permeation but also effectively repelled foulants during filtration. Remarkably, the gravity-driven permeation flux of the superhydrophilic membrane reached as high as 30,000 L·m^-2·h^-1. Furthermore, this superhydrophilic membrane demonstrated reasonable separation efficiency, achieving removal rates of 60.0% for total suspended solids, 93.1% for Melosira, and 83.0% for poly(vinyl alcohol). Upon heating at 100 °C for 1 h, the membrane surface reverted to a superhydrophobic state, enabling self-cleaning during membrane maintenance. With its facile preparation and smart electro- and thermo-responsive properties, this copper-based membrane, featuring reversibly switchable wettability, holds great promise for scalable applications in water treatment.